Field of the Invention
The present invention relates to moving object recognition systems, moving object recognition programs, and moving object recognition methods for recognizing moving objects by using single-view images.
Description of the Related Art
There have been known moving object recognition systems that recognize moving objects existing near a vehicle, and then report to or alert the driver or automatically perform braking on the vehicle (hereinafter referred to simply as “reporting”). The distance from the vehicle to a moving object can be directly measured by using a distance sensor such as a millimeter-wave radar, or can be measured by performing image processing with a stereo camera. The moving direction of the moving object and the velocity of the moving object relative to the vehicle can be determined by arranging measured distances in chronological order and then analyzing those distances. As the moving direction of the moving object and the velocity of the moving object relative to the vehicle are determined, the probability (risk) of the moving object colliding with the vehicle can be calculated, and reporting can be performed in accordance with the risk.
As simpler and less expensive moving object recognition systems, there also have been systems that recognize a moving body with a monocular camera that has only one line of an optical system and an imaging element. Such a system continuously captures images with a monocular camera, to obtain single-view images arranged in chronological order. The technique disclosed in U.S. Pat. No. 8,184,857 which is incorporated herein by reference is known as a technique for detecting a moving object from such single-view images.
By the technique disclosed in U.S. Pat. No. 8,184,857, feature points are extracted from each of single-view images arranged in chronological order, and the feature points are grouped by moving objects, based on the motion vectors (optical flows) of the extracted feature points. The grouping is performed based on variations in the convergence properties of the optical flows to a vanishing point and the external ratios. In this manner, accurate moving object detection can be performed, even if there is an inaccurately-calculated optical flow.
In an in-vehicle moving object recognition system, it is preferable to report only the risk of a moving object colliding with or rushing toward the vehicle to the driver, without reporting any moving object with no risk of collision to the driver. This is because reporting every moving object bothers the driver, and might adversely affect the driving.
In such an in-vehicle moving object recognition system, the reliability of a result of recognition processing does not always match an actual risk of collision. That is, the risk of collision might be zero, though the result of recognition processing shows a high level of reliability, and vice versa. Information that is useful to most drivers is not the information about the reliability of recognition processing but the information about the risk of a recognized moving object colliding with his/her own vehicle.